A known example of a fixing apparatus mounted in electrophotographic copiers and printers is a fixing apparatus using a film heating system. The film heating fixing apparatus includes a tubular film, a heater in contact with the inner surface of the film, and a pressure roller that forms a nip with the heater, with the film therebetween. The heater is held by a heater holder made of resin. The heater holder is reinforced by a metal reinforcement.
The heater holder has a through-hole in part in the longitudinal direction, through which a temperature detecting element disposed in a space between the heater holder and the reinforcement senses the temperature of the heater. The heater is controlled according to the temperature sensed by the temperature detecting element. The space between the heater holder and the reinforcement further accommodates a protection element, such as a thermal switch and a thermal fuse. The protection element also senses the heat of the heater through another through-hole in the heater holder. The protection element has a function of interrupting power to the heater when the heater overheats (PTL 1).